Flareless fittings have been in use for decades for conduits such as tubes and pipes. A flareless fitting is used to connect or join two tube or pipe ends or to connect a conduit end to another assembly such as a tank, a valve, a manifold and so on. The applications are as varied as the types of assemblies with which the fittings are used. One very common type of flareless fitting is a ferrule type fitting. In a ferrule type fitting, one or more ferrules are used to join or connect a conduit end to a fitting member, typically called a fitting body. The fitting body may then be joined to (or be part of) another assembly. In a ferrule type fitting, the ferrule or ferrules must establish a fluid tight seal, particularly under pressure, as well as adequate grip of the conduit and protection against vibration fatigue. High performance fittings, such as are available from Swagelok Company, Solon, Ohio, are capable of withstanding pressures many times the rated pressure of the fitting without leaking, without vibration fatigue and without conduit blow out to the point that the conduit will burst before a seal is compromised or the ferrule(s) may lose their grip on the conduit.
Ferrule style fittings have an advantage over other end connections in that they do not rely on any special preparation of the tube or pipe end, other than low cost squaring and deburring. This is because the ferrules create the seals and tube grip.
Lower cost markets, such as the automotive industry, have their own performance requirements for fluid connections. Most notably, automotive assembly requires simpler assembly procedures. The automotive industry has resisted using ferrule type fittings not only for cost reasons, but also for assembly needs. Typical ferrule type fittings are assembled by what is commonly known as pull-up by turns. Two threaded components, such as a nut and body, enclose the conduit end and one or more ferrules. The assembly is first tightened to a finger tight condition and then a prescribed number of turns, such as one and a quarter or one and a half turns, are used to pull-up the fitting to its assembled condition. The number of turns is carefully prescribed to prevent over torque or inadequate pull-up. The automotive industry on the other hand typically wants to assemble parts by torque. This allows a simple torque wrench or tool to be used to make the final assembly with the assurance that the final assembly has been properly assembled.